The Priority Document, Japanese Patent Application No. Hei4-342612 filed in Japan on Dec. 22, 1992 is hereby incorporated hereinto by this reference.
1. Field of the Invention
The present invention relates to a sealing apparatus. Particularly, the present invention relates to the sealing apparatus which can reduce the noise occurring from the sliding of a piston and the like.
2. Description of the Art
Conventional sealing apparatus are described in U.S. Pat. No. 5,162,441 and Japanese Patent Publication No. Hei2-60901.
One such conventional sealing apparatus such as a piston cup is made of a rubber compound such as ethylene propylene rubber (EPDM), and the hydraulic fluid tightness (basis of the hydraulic oil is a variety of glycol) of the EPDM is high.
However, when the rubber compound is mounted on a piston, noise was likely to result. The noise is caused by vibration which results from the inner wall cylinder sliding well with other apparatus. The noise occurs mainly in the 500-2500 Hz range.
it is an object of the present invention to provide a sealing apparatus which reduces the sliding noise.
To reduce the sliding noise, the sealing apparatus is made of rubber compounds which the rubber polymer includes alkyl lateral chain, and at least a part of alkyl group hydrogen, of a rubber polymer in the cortex, is substituted by fluorine.
Other objects, features, and characteristics of the present invention, as well as the method of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein the same reference numerals designate corresponding parts in the various figures.